Stretching apparatus for screen cloth



9 G. A. OVERST ROM ET AL 2,223,267

' STRETCHING APPARATUS FOR SCREEN CLOTH' Filed April 13, 1940 Illlllll I IN V EN T 0R5 6067A VE A. Ovs'es TEOM, By GEoea-E Ova-esreav,

CON 0 v5 E M, (3m

TORNEYS.

Patented Nov. 26, 1940 .11: V I -Gustave A. Overstrom and George Overstrom,

, Eagle Rock, andConrad overstrom, Altadena,

Calif.

Application April 13,

Claims.

i This invention relates to improvements in stretching apparatus for screen cloth of the type illustrated by the patent to Gustave A. Overstrom, No. 2,136,950, issued November 15, 1938 The main object of the invention is to provide a screen stretching bar and a liner bar therefor in which the liner bar is held in place independently of the stretching bar.

A further object of the invention is to provide stretching apparatus for a screen cloth in which the stretcher means is free to slide into engagementwith the cloth to stretch said cloth independently of and without regard to the position of the liner bar.

A further object of the invention is to provide means, independent of each other, for holding a liner bar and a stretcher bar in slidable contact.

A further object of the invention is to provide 'a liner bar that is easily removable from the machine withoutdetachment from a stretching bar.

A further object of the invention is to provide spring means for holding the liner bar down firmly on' top of and in frictional contact with the screen cloth when it is being stretched. Heretofore, when apparatus of this character was used, the stretcher bar would slide into engagement with'thecloth, and the liner bar, being attached thereto; of necessity would have to be adjustable. It was found in practical operation thatwhen the liner bar was bolted to the stretcher bar,operators would not unloosen the linerbar from thes'tretcher .bar when additional stretching of the cloth was required; and as a result the liner bar acted as an effective stop and would not permit the stretcherbar to freely move into engagement With-the cloth to effect further stretching. This was particularly found true when the stretching apparatus was used in screen structure's employed to screen rotary drill mud. This mud oftencarries an acid in it that corrodes the threads of bolts and nuts, making it diffi cut for the operator to loosen the same so that free movement of the stretcher bar could be had, and as a consequence they frequently met difficulty in using a liner bar structure such as'is illustrated by Patent No. 2,136,950.

, .In the construction as illustrated in Patent No. 2,136,950, 7 the liner bar is attached to the stretcher bar by means of bolts embedded in and carried by the stretcher bar, and the liner bar is boltedto the stretcher bar after the stretcher bar had effected its operation of stretching the cloth. This invention entirely does away with the bolts; and attachments carried by the 1940, Serial No. 329,446 (01. 209-403) stretcher bar to effect fastening of the liner bar thereto.

This invention resides substantially in the, combination, construction, arrangement and relative location of parts, all in accordance with this disclosure.

Referring to the accompanying drawing and to the various views and reference signs appearing thereon:

Figure l is a plan view of a screening apparatus with parts broken away, showing the liner bar and the stretcher bar of this invention;

Figure 2is an elevation of Figure 1 with parts broken away; sho ng the stretcher bar;

Figure 3 is an enlarged cross-sectional view of Figure 2, taken along the line 3-3 of Figure 2,

looking in the direction of the arrow with some 'parts'broken away; and

Figure 4 is an enlarged side elevation of th liner bar with a portion broken away.

In the drawing the same part is designated by the same reference sign.

Referring now to the drawing in detail, there is illustrated somewhat diagrammatically a screen structure illustrating the manner of application of this invention thereto. The structure is illustrated as comprising a support consisting o-f a pair of side frames I made of any suitable material, such as metal. The ends 2' of the coil springs 2 are bolted to the tops of the side frame members I. There are four of these springs longitudinally spaced in pairs to provide a support for the screen box 4. This screen box is provided with brackets 3', secured thereto in any suitable manner; havingpintles 3 attached to the inner ends of the coil springs 2. Thusthe screen box issupported at its four corners.

Thelscreen box is made up of side channels, as is clear from the figures, which are interconnected by cross-braces 8, 9 and ID of any suitable shape; all of these parts being made of iron. or steel and preferably Welded together into a rigid structure. Extending longitudinally of the cross-braces and resting or attached thereon are the rails or bars. and I2. The bars II are positioned close to the side frame channels in parallel relation therewith but spaced therefrom, as is clear from Figure 3. There are two or more of ,the rails I2, depending upon the width of the screen box. Secured to the side frame channels are the brackets l in which is secured a tubular housing 6 within which are sealed bearings in which an unbalanced shaft 5 is journalled for rotation. This shaft is provided with a pulley 5 by means of which it may be rotated from any suitable external source of power. The rotation of the shaft 5 in the direction of the arrow, as indicated in Figure 2, effects vibration of the screen box in a closed curved path which lies substantially in a vertical plane.

In the screen box and forming the floor thereof is the screen cloth 4' which rests on the bars II and I2, which'sare preferably slightly curved longitudinally, as indicated in Figure2. The bars I2 have secured on the tops thereof resilient supports I2 for the screen cloth 4' in accordance with well known practice in the'art. U r j The screen cloth is stretched transversely of the screen box by meansof stretching mechanism of the general type disclosed inftheabovementioned patent but ina'ccordance"with this invention modified as will now be described. A pair of stretcher bars I3 having longitudinally curved lower edges lie along the inner faces of the side frame channels of the screen box' I and are engaged alongtheir top edges by means of vertically adjustable bolts I3. The space between'the side frame channels and the bars I I is'such that when the stretcher bars move down between them, with the side edges of the screen cloth 4 extending around the loweredges ofv the stretcher bars, a friction fit, will result. Thus as the stretcher bars are moved downwardly the screen cloth 1 is drawn tight transversely.

Lying along the inner faces of the stretcher bars I3 are the liner bars M which are likewise longitudinally curved along their lower edges so as tomate with the longitudinal curve of the bars II. The liner bars I4 are supported by a plurality of spring strips I5 which are riveted to them by the rivets I6 which engage plate washers I1 nested into the liner bars so as to be flush with the outer faces thereof. The upper. ends of the spring supports I5 overlie the top flanges of the sideframe channels. Clamping plates I5 engage these upper overlying ends of vthe springs I5 and are bolted to the side frame, channels by the nuts and bolts I8.

H By means of this construction it will be seen that the stretcher bars I3 move up, and down independently of the liner bars I4 which are spring-pressed against the stretcher bars and are positioned vertically. so as to rest under spring tension on the top adjacent surfaces of-the screen cloth. These liner bars serve to prevent unscreened material from running down on the cloth over the rail I I, as well as, preventing abrading material from lodging between the cloth and rail II and stretcher bar I3.

1 The screen cloth is originally inserted, or an old cloth is replaced by a new one, by substantially the following procedure: The stretcher bars I3 and the liner bars I4 are removed from the screen box. The cloth to be inserted is laid out fiat ona suitable surface. It comes, of course, somewhat wider than the distance between the inside faces of the side frame members 4 of the screen box. The longer side edgesof the screen are bent at right angles out of the plane of the cloth so that the space between the flanges thus formed is equal to the distance between the inside faces of the sides 4 of the screen box. The width of the flanges thus formed is the same. along both edges and throughout their length. The cloth will, of course, maintain this shape because as commonly used in the art it is of metal, being .woven of wire strands of suitable size.

The screen cloth is then inserted in the machine with its flanges extending upwardly. The stretcher bars. I3 are then placed in .the machine place. cloth can be changed by properly adjusting the so that the upturned flanges of the cloth lie between the stretcher bars and the channel faces, as will be clear from Figure 3. The screws I3 are then tightened down and since they engage the top edges of the stretcher bars I3 they force these bars down into the space between the channels 4 and the rails II, Ihe cloth is thus caused to take the shape clearly shown in Figure 3, and as the stretcher bars move downwardly they cause the cloth to stretch transversely and become taut. The liner bars I4 are then put in At any time the tension in the screen screws I3. 7

It will be seen from the above that the features ofthe screen'cloth stretching mechanism of the patent above-mentioned are retained in this mechanismwhile the cloth stretching parts are protected.

While a preferred embodiment of the invention has been disclosed and described herein, it is to be understood that those skilled in theart will appreciate many changes and modifications which can be made without departing from the spirit and novel scope of the invention herein disclosed. We do not, therefore, desire to be limited by the foregoing description,:but rather by the scope of the claims granted us.

What we claim is:

1. In a vibrating screen structure, a screen box having side members, longitudinal supports in said screen box extending parallel to but spaced from the side members, a screen. cloth for the screen box and resting on said longitudinal supports, stretcher bars engaging the side edges of the screen cloth to frictionally clamp them between the side members and the longitudinal supports, and spring supported liner bars. pressed against the sides of said stretcher bars and on top of the adjacent areas of the screen cloth.

2. In a vibrating screen structure, a screen box having side members, longitudinal supports in said screen box extending parallel to but spaced from the side members, a screen cloth in the screen box and resting on'said longitudinal supports, vertically movable stretcher bars engaging the side edges of the screen cloth frictionally between the frame members and the longitudinal supports, and resiliently supported liner bars held in contact with the sides of said stretcher bars, so that the stretcher bars may be adjusted vertically independently of the liner bars.

3. In a vibrating screen structure, a screen box having side members, longitudinal supports in said screen box extending parallel to but spaced from the side members, a screen cloth resting on said longitudinal supports, vertically movable stretcher bars engaging the side edges ofthe screen cloth frictionally between the frame members and the longitudinal supports, liner bars lying against the inner faces of the stretcher bars, and supports for attaching the liner bars to the side members whereby the stretcher bars may be moved independently thereof.

4. In a vibrating screen structure, a screen box having side members, longitudinal supports in said screen box extending parallel to but spaced from the side members, a screen cloth resting on said longitudinal supports, vertically movable stretcher bars engaging the side edges of the screen cloth frictionally between the frame members and the longitudinal supports, liner bars lying against the inner faces of the stretcher bars, and spring supports secured to the liner bars and to the side members for holding the rection, and resiliently supported liner bars frictionally engaging the stretcher bars While permitting independent movement thereof.

GUSTAVE A. OVERSIROM. GEORGE? OVERSTRO M. CONRAD OVERSTROM. 

